The beam must be extracted into the air through the vacuum window to irradiate the living cell.In the window design,the material and thickness must be chosen to compromise the beam spot size broadening and the window safety.The structure-static analysis on the window of different structures and materials is done with the finite element analysis method,and the deformation and the equivalent stress are simulated.The safety of these candidates is investigated using the intensity theory.In addition,the small angle scattering and the transverse range of ions are simulated using SRIM code,including all the effects on the beam spot size broadening,such as the incident ion energy, the material and the thickness of the window and the air composing.At last,the appropriate vacuum windows are presented,including the structure,material and thickness.
